A thermal expansion valve as a throttling device is widely used in a loop of a refrigeration system, and is used to control the flow of refrigerant by sensing the temperature and the pressure of the refrigerant at a specific position. With the continuous popularization of a commercial refrigerating device, the thermal expansion valve is also widely used in a commercial refrigeration system with a large capacity.
In the conventional technology, in a case that a pipeline extending from an evaporator and a condenser to a compressor is relative long (longer than 25 meters) in a refrigerating system, a check valve is required to be arranged in parallel to the thermal expansion valve (the direction of the check valve is opposite to that of the expansion valve), so as to improve the operational stability of the system. The flow direction in the check valve is opposite to the flow direction in a valve port of the expansion valve, and when refrigerant in the system flows in a forward direction (flowing from an inlet to an outlet), the check valve is closed by pressure difference and the thermal expansion valve functions; and when the refrigerant in the system flows in a reverse direction, the check valve is opened by pressure difference and the thermal expansion valve dose not work. However, the check valve and bypass passages which are separately arranged may increase the costs for assembly and maintenance, and increase the risk of potential leakage.
In view of this, recently, in order to simplify the components of the refrigerating system, a method of replacing the expansion valve and the check valve, which are separately arranged, with a thermal expansion valve with one-way control function is widely used in the refrigerating system. Chinese patent application No. CN200310103606 discloses a thermal expansion valve, and as shown in FIG. 1, the thermal expansion valve includes a valve body 54′ on which an inlet passage and an outlet passage are provided. An inner cavity 40′ is provided in the valve body 54′ and is in communication with the inlet passage and the outlet passage. A valve port 42′ is provided in the inner cavity 40′. A temperature sensing component 30′ is arranged at one end of the valve body 54′ to close the inner cavity 40′. A valve core component is placed in the inner cavity 40′, and has a valve rod 32′ abutting against the temperature sensing component 30′, and a valve core 33′ cooperating with the valve port 42′ to control the flow of fluid medium flowing from the inlet passage to the outlet passage. A nut cover 64′ is further mounted in the valve body 54′, and is provided with an accommodating hole 48′ in communication with the inner cavity 40′. A valve core 70′ is arranged in the accommodation hole 48′, and an auxiliary valve port 50′ is machined on the valve body 54′. When the medium flows from the inlet passage to the outlet passage, the auxiliary valve port 50′ is closed; and when the medium flows from the outlet passage to the inlet passage, the auxiliary valve port 50′ is opened.
Apparently, the above structure may integrate the expansion valve and the check valve which are separately provided as an integrated structure, however an opening is required to be additionally machined on the valve body for arranging the nut cover and the check valve, which is prone to cause leakage of the expansion valve and directly reduces the reliability of the product. Furthermore, this structure is complicated and has a high requirement for processing technology.
In view of this, it is urgent to optimize the structure of the conventional thermal expansion valve having the check valve to improve the manufacturability and the operational reliability.